Land Rover Repair: top end rattle clicking disco 2 v8, hydraulic tappets, cam follower

Question
Tappet preload keeps on coming up as the possible cause of my top end rattle on my disco series 2 v8. i dont believe it is mentioned in the disco workshop manual as something important.I have renewed all the bottom end including lifters,cam etc.head recoed. only old parts are the rockers pushrods and rocker shafts.My cam is non standard .What do you think it could be?     Thanks Rob.

Answer
Hi Rob,

to be honest, this is work I've yet to perform.  I've looked around and some have suggested problems with hydraulic tappets (cam follower).

I've heard exhaust manifold leaks that sound like tappet trouble.  Could this be possible?  Carefully feel around the Y pipe for cracks (when cold) or blasts of air when running.

Regards,

JohnMc